Question

Tìm x biết

a,\(\left(\frac{4}{5}\right)^{2x+7}\text{=}\frac{625}{256}\)

b,\(\frac{7^{x+2}+7^{x+1}+7^x}{57}\text{=}\frac{5^{2x}+5^{2x+1}+5^{2x+3}}{131}\)

c,\(\left(4x-3\right)^4\text{=}\left(4x-3\right)^2\)

d,\(\frac{2x+3}{5x+2}\text{=}\frac{4x+5}{10x+2}\)

e,\(\frac{3x-1}{40-5x}\text{=}\frac{2x-3x}{5x-34}\)

f,\(\frac{15}{x-9}\text{=}\frac{20}{y-12}\text{=}\frac{40}{z-2x}\) và \(xy\text{=}1200\)

Answer 1

a)\(\left(\frac{4}{5}\right)^{2x+7}=\left(\frac{4}{5}\right)^4\)

=> 2x + 7 = 4 

     2x        = 4 - 7 

     2x        = -3

       x        = -3 : 2

       x         = -1,5

   Vậy x = -1,5